1. Field of the Invention
The present invention relates to an electrophotographic photoreceptor, a photoreceptor supporting device, an imaging device and a process cartridge. In particular, the present invention relates to the photoreceptor supporting device which is configured to support the electrophotographic photoreceptor. The present invention farther relates to the imaging device in which an image formed on the electrophotographic photoreceptor is transferred directly or indirectly through an intermediate transfer body, and then the image is recorded on a recording material. The imaging device is used in such as a copy machine, a printer, a facsimile, or a complex machine of those. The present invention further relates to the process cartridge which includes the electrophotographic photoreceptor integrated with at least one of a charging device, a developing device and a cleaning device, and which is provided in the imaging device.
2. Description of the Related Art
Conventionally, in an electrophotographic type imaging device, after a surface of an electrophotographic photoreceptor is charged evenly by a charging device, with rotation of the electrophotographic photoreceptor, writing is performed by an exposure device and an electrostatic latent image is formed, and then with a developing device the electrostatic latent image is visualized by adhering toner, and an image is formed on the electrophotographic photoreceptor. The image is then transferred directly) or indirectly through an intermediate transfer body, and then the image is recorded on a recording material such as paper or a resin film.
In such an imaging device, in general, the electrophotographic photoreceptor is supported rotatably by a photoreceptor supporting member through a photoreceptor shaft which penetrates through a shaft center. For example, each of two flanges 2 and 2 is attached to each opening of both ends of a cylindrical photoreceptor pipe 1, as illustrated in FIG. 6A, one photoreceptor shaft 4 penetrates through each of the centers of the flanges 2 and 2 through respective one of hearings 3 and 3, the flanges 2 and 2 are supported rotatably on the photoreceptor shaft 4, and both ends of the photoreceptor shaft 4 are fixed and supported by a couple of photoreceptor supporting members 5 and 5 respectively, the couple of photoreceptor supporting members 5 and 5 being disposed opposed to each other.
In addition, as illustrated in FIG. 6B, for example, each of two flanges 2 and 2 is attached to each opening of both ends of the cylindrical photoreceptor pipe 1, one photoreceptor shaft 4 penetrates through each of the centers of the flanges 2 and 2 and is retained to be rotated together with the flanges 2 and 2, and both ends of the photoreceptor shaft 4 are supported rotatably by a couple of photoreceptor supporting members 5 and 5 which are disposed opposed, respectively, through respective one of bearings 3 and 3.
In addition, an earth member 6 is stored in one of the flanges 2 and 2, for example, the one on the right side in the figure, and a first contact part 6a which contacts an inner circumference of the photoreceptor pipe 1 is formed at one end, and a second contact part 6b which contacts an outer circumference of the photoreceptor shaft 4 is formed at another end, in the photoreceptor supporting device illustrated in FIGS. 6A and 6B. Here, it is possible for two earth members 6 and 6 to be provided. Moreover, a leading end of an electrical conduction member 7 is elastically pressed against an end face of the photoreceptor shaft 4.
However, problems arise such as the structure is complex, and the photoreceptor shaft 4 of φ8 mm to φ10 mm is necessary to secure the rigidity, and the cost is high, and wear-out at the second contact part 6b is remarkable, for the photoreceptor supporting device illustrated in FIGS. 6A and 6B. That is, due to a stick material generally used as the photoreceptor shaft 4 being φ8 mm or more in consideration of the rigidity, etc., the wear-out of the second contact part 6b which contacts the outer circumference of the photoreceptor shaft 4 and slides thereon is remarkable, and a conduction assistance material such as conductive grease, a conductive brush, or a carbon terminal or the like is often necessary.
In a conventional imaging device, as illustrated in FIG. 6C, an electrophotographic photoreceptor is supported by cantilevered photoreceptor shafts 8 and 8, instead of the photoreceptor shaft 4 which penetrates through the shaft center, an end of each of the photoreceptor shafts 8 and 8 being retained by the respective photoreceptor supporting member 5. However, in such a photoreceptor supporting device, due to falling of the cantilevered photoreceptor shafts 8 and 8 or the like, leaning or falling of a shaft center of the electrophotographic photoreceptor occurs, and thus problems arise such as easy occurrence of inclination of an image, easy occurrence of distortion of the image resulting from swinging of the photoreceptor by a rotation, and wear-out at the second contact part 6b. 
Therefore, a photoreceptor supporting device with the following structure is proposed, for example, as illustrated in FIG. 7. Namely, each of two flanges 2 and 2 is attached to each opening of both ends of a cylindrical photoreceptor pipe 1, a shaft part 2a projecting outward from the end of the photoreceptor pipe 1 at a shaft center position thereof is formed at each flange 2, and the shaft parts 2a and 2a are directly supported rotatably by the photoreceptor supporting members 5 and 5 through respective one of bearings 3 and 3, without through the photoreceptor shaft.
In addition, in such a photoreceptor supporting device, a bracket 9 is attached to the photoreceptor supporting member 5 on one side, for example on the right side in FIG. 7, and the end of one of the cantilevered photoreceptor shafts 8 and 8 (for example the one on the right side in FIG. 7), is retained by the bracket 9. Further, at least one earth member 6 is provided, and a first contact part 6a which contacts an inner circumference of the photoreceptor pipe 1 is formed at one end, and a second contact part 6b which contacts an outer circumference of the cantilevered photoreceptor shaft 8 is formed at another end of the earth member 6, moreover, a leading end of an electrical conduction member 7 is elastically pressed against an outer end face of the photoreceptor shaft 8, and an electrical connection is formed.
However, even with this structure, problems still arise, such as a complicated structure and high cost, and many contact parts being required for electrical connection, remarkable wear-out at the second contact part 6b, and decrease of the reliability of the conduction.